Continuous symmetries generated with observables of a quantum theory in theMinkowski spacetime are discussed. An example of an originated in this wayalgebra of observables is the algebra of observables of the canonical quantumtheory, that is contained the Lorentz group algebra

We analyse a class of non-Hermitian Hamiltonians, which can be expressedbilinearly in terms of generators of a sl(2,R)-Lie algebra or their isomorphicsu(1,1)-counterparts. The Hamlitonians are prototypes for solvable models ofLie algebraic type. Demanding a real spectrum and the existence of

Finding feasible points for which the proof succeeds is a critical issue insafe Branch and Bound algorithms which handle continuous problems. In thispaper, we introduce a new strategy to compute very accurate approximations offeasible points. This strategy takes advantage of

We consider the alternating sign matrices of the odd order that have somekind of central symmetry. Namely, we deal with matrices invariant under thehalf-turn, quarter-turn and flips in both diagonals. In all these cases, thereare two natural structures in the

Scattering at a central potential is completely characterized by the phaseshifts which are the differences in phase between outgoing scattered andunscattered partial waves. In this letter it is shown that, for 2D scatteringat a repulsive central potential, the phase shift

We consider a gradient interface model on the lattice with interactionpotential which is a nonconvex perturbation of a convex potential. Using atechnique which decouples the neighboring vertices sites into even and oddvertices, we show for a class of non-convex potentials:

We consider the annealed asymptotics for the survival probability of Brownianmotion among randomly distributed traps. The configuration of traps is given byindependent displacements of the lattice points. We determined the asymptoticsfor the logarithm of the survival probability up to multiplicative

We study 12 parameter families of two qubit density matrices, arising from aspecial class of two-fermion systems with four single particle states oralternatively from a four-qubit state with amplitudes arranged in anantisymmetric matrix. We calculate the Wooters concurrences and thenegativities

Let $R$ be a commutative ring and $\Gamma(R)$ denote its zero-divisor graph.In this paper, we investigate the genus number of the compact Riemann surfacewhich $\Gamma(R)$ can be embedded and illustrate all finite commutative rings$R$ (up to isomorphism) such that $\Gamma(R)$

The paper studies a single-server queueing system with autonomous service and$\ell$ priority classes. Arrival and departure processes are governed by markedpoint processes. There are $\ell$ buffers corresponding to priority classes,and upon arrival a unit of the $k$th priority class occupies

Recall that the usual Einstein metrics are those for which the first Riccicontraction of the covariant Riemann curvature tensor is proportional to themetric. Assuming the same type of restrictions but instead on the differentcontractions of Thorpe tensors, one gets several

An old theorem of Charney and Lee says that the classifying space of thecategory of stable nodal topological surfaces and isotopy classes ofdegenerations has the same rational homology as the Deligne-Mumfordcompactification. We give an integral refinement: the classifying space of

The Local Fourier analysis (LFA) is a classic tool to prove convergencetheorems for multigrid methods (MGMs). In particular, we are interested inoptimality that is a convergence speed independent of the size of the involvedmatrices. For elliptic partial differential equations (PDEs),

The most commonly known triangulated categories arise from chain complexes inan abelian category by passing to chain homotopy classes or invertingquasi-isomorphisms. Such examples are called `algebraic' because they originatefrom abelian (or at least additive) categories. Stable homotopy theory producesexamples of

This paper is a tutorial in a general and explicit procedure to simplifysemidefinite programs which are invariant under the action of a symmetry group.The procedure is based on basic notions of representation theory of finitegroups. As an example we derive

Inference based on the penalized density ratio model is proposed and studied.The model under consideration is specified by assuming that the log--likelihoodfunction of two unknown densities is of some parametric form. The model hasbeen extended to cover multiple samples problems

We prove a necessary optimality condition of Euler-Lagrange type forvariational problems on time scales involving nabla derivatives ofhigher-order. The proof is done using a new and more general fundamental lemmaof the calculus of variations on time scales.